Contact cleaning



Dec. 3, 194 R GQETZ 2,223,516

CONTACT CLEANING Filed March 30, 1939 INVENTOR [aw/611m 606/2 ATTORNEY Patented Dec. 3, 1940 UNITED STATES CONTACT CLEANING Lawrence R. Goetz, Indianapolis, Ind., assignor to P. R. Mallory & (30., Inc., Indianapolis, Ind., a corporation of Delaware Application March 30.

1 Claim.

This invention relates to improved methods of producing interrupter contact assemblies and particularly electromagnetic vibratory interrupter devices.

An object of the invention is to improve methods of production of such devices.

Another object of the invention is to provide an improved method of contact cleaning.

Other objects of the invention will be apparent 10 from the following description and accompanying drawing taken in connection with the appended claim.

The invention comprises the features of construction, combination of elements, arrangement 15 of parts, and methods of manufacture and operation referred to above or which will be brought out and exemplified in the disclosure hereinafter set forth, including the illustrations in the drawing.

In the drawing, the figure of the drawing is a diagram of a preferred circuit arrangement for use in carrying out the present invention.

A feature of the present invention resides in a method of electrically cleaning vibratory inter- 26 rupter contacts, preferably after the vibratory interrupter has been completely assembled and sealed. According to this method the interrupter contacts are operated in a circuitcapable of discharging an arc current between the con- 80 tact pairs of the assembly whereby to consume or disperse deleterious foreign material which would otherwise interfere with the proper opera.- tion of the contacts.

While a preferred embodiment of the inven- 35 tion is described herein it is contemplated that considerable variation may be 'made in the method of procedure and the construction of parts without departing from the spirit of the invention. In the following description and in 40 the claim, parts will be identified by specific names for convenience, but they are intendedto be as generic in their application to similar parts as the art will permit.

This invention has particular application to 45 the production of electromagnetic vibratory interrupter devices commonly known as vibrators, which are used, for example, in systems for converting low potential direct current into high potential currents for use as biasing potentials in 50 radio sets and the like. Such a device ordinarily comprises a vibratory reed actuated by an electromagnet and having reed contacts. cooperating with relatively stationary contacts to intermittently interrupt an electric circuit in which is 55 located a source of low voltage direct current.

1939, Serial No. 264,992

The electromagnet, reed and contacts are usually mounted on a suitable frame and the assembly is then sealed in a metal can or other container having suitable external terminals for connection into the circuit in which it is to be 5 used. In practice the parts are carefully assembled and inserted in the can or container and then sealed within the container, for example, by closing the mouth of the container with a disc carrying terminal prongs and spinning the edge of the can over the disc. After the vibrator is thus assembled it is, of course, impossible to reach the contacts for cleaning or adjustment.

Heretofore, even with the most careful production and inspection of the units prior to and during assembly a considerable amount of difficulty has been experienced when the vibrators were connected in the circuit in which they were intended to be used and attempted to be operated. Under these" conditions many starting failures have been encountered.

It appears that these failures have largely been dueto the presence of small amounts of impurities and foreign matter on the contacts which'prevented a good electrical contact from being obtained when two contacts of a pair were brought together by the vibration of the reed. Such foreign matter may comprise particles of dust, metal oxide and probably a. certain amount of oil.

I have now discovered a method of remedying this difllculty. My method comprises operating .the vibrator for a short period of time in an electric circuit which produces a strong arcing current between co-operating contacts. This 85 current apparently burns away the foreign ma terial or drives it from the face of the contacts thereby cleaning them and producing subsequent satisfactory operation of the contacts.

- The preferred circuit arrangement for this purpose is shown in the figure of the drawing. In this figure, the completed sealed vibrator assembly 5 is shown diagrammatically. This assembly comprises a vibratory reed l actuated by electromagnet 2 having a high resistance winding and alternately closing contact pairs 3 and 4.

In the normal rest position of the reed both contact pairs are open.

- This mechanical assembly is sealed within metal can [5 by insulating disc cap 6 carrying external contact prongs 1 connected respectively to the reed and its co-operating contacts. The winding of electromagnet 2 is connected across the contact pair 3.

In order to clean contact pairs 3 and l the vibrator is connected in the electrical circuit shown in the lower half of the figure. This circuit comprises a transformer 9 having a primary winding l0 and a secondary winding ll. Low voltage battery 8 is connected between the center tap of primary winding l0 and the reed i of the vibrator as well as to one end of the electromagnet winding. The two ends of primary winding H) are connected respectively to the two stationary contacts of the vibrator, the right hand end also connecting to the other end of the electromagnet winding. Thus it willbe seen that current from battery 8 will first traverse a circuit including high resistance winding of electromagnet 2 and half of primary winding I0 thereby energizing the electromagnet. This attracts reed I so as to close contact pair 3, the contacts thereby short-circuiting the high resistance electromagnet winding and allowing a strong pulse of current to flow in the right-hand half of the primary winding of the transformer. Upon deenergization of the electromagnet the reed swings back and closes-contact pair 4, giving a current pulse in the left hand half of primary l0 after which the cycle is repeated.

The secondary winding ll of the transformer is connected to a resistance load I! shunted by a timing capacitance 13 which synchronizes the transformer current with the vibrations of the reed.

A second capacitance I4 of a high capacity value is connected directly across the primary winding H] of the transformer. This capacitance should be preferably of a low power factor type and of comparatively high capacity such as, for example, 40 mfds.

When the circuit is connected as shown the vibrator begins to operate. The secondary circuit of the transformer provides a normal load on the system such as would ordinarily be encountered in normal use of the vibrator. At the same time high capacitance l4 produces a strong discharging current across the contact pairs 3 and 4 as they are opened by the vibrations of the reed, thereby maintaining a small arc across these contacts for part or all of each operating cycle. It is this are which effects the cleaning of the contacts.

Such an arc will, of course, cause deleterious contact pitting and'transfer of the contact material if allowed to continue for a sufficiently long period of time. Accordingly, the vibrator is operated in the circuit illustrated for' only a short time, such as from 1 to 6 seconds. This period of operation is sufficient to effect the desired cleaning of the contact surfaces but the contacts themselves will not be deleteriously affected by this short operation.

It will be obvious that the size of capacitance used and the length of time of operation for cleaning will depend upon the other circuit conditions provided and the size, frequency and de sign of the vibrator itself.

The present process has the advantage of cleaning the contacts after the vibrator is completely assembled and sealed so that there is no danger of subsequent accumulation of dirt or foreign matter on the contacts. Likewise it is thus possible to correct the operation of vibrators which might otherwise be rejected or have to be replaced.

While the present invention, as to its objects and advantages, has been described herein as carried out in specific embodiments thereof, it is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of the appended claim.

What is claimed is:

The method of improving the operation of an electromagnetic vibratory interrupter of the type adapted for use in power supply systems for producing high voltage currents from a low voltage D. C. supply, which comprises operating the vibrator by vibrating the vibratory element under control of the electromagnet so as to periodically open and close the interrupter contacts and discharging a strong arcing current across each contact pair as they are opened and maintaining the are for at least a part of the operating cycle, said arcing current being of higher current value and persisting throughout a greater part of the open-contact period than currents encountered in the normal useful operation of the interrupter and being capable of dispelling foreign material from the contact surfaces in at most a few seconds of operating time.

LAWRENCE R. GOETZ. 

